1. Field of the Invention
The present invention relates to a method of and apparatus for supporting a rope of a crane of the type having an articulating structure.
2. Description of the Prior Art
Conventional cranes such as bridge cranes have a structure carried by tall legs or supports. The structure is usually divided into three sections: namely, an end boom section, a base boom section and a main girder section. The end boom section and the base boom section in combination constitute an elevation structure. These sections are pivotally connected in series at their opposing ends by means of shafts, so that each girder section can pivot relatively to the adjacent one or ones. A hoisting rope is extended along the structure. A trolley having a hoisting tackle suspended from the hoisting rope is adapted to run along the structure from one section to another. This type of crane is shown, for example, in the specification of U.S. Pat. No. 3,325,018. When the operation of the crane is suspended, the crane is made to rest with its elevation structure folded such that the end boom section is extended horizontally while the base boom section is made to stand upright. As the elevation structure of the crane is folded in this manner, the hoisting rope is slacked largely and hung from the main girder section and the end boom section dangerously. In order to avoid this danger, it is conceiveable to support the hoisting rope by a suitable rope support so as not to permit the rope to hang. Attaching of such rope support, however, may form an obstacle which impairs linear and smooth running of the cargo trolley over the entire length of the structure.
Another solution is disclosed in, for example, Japanese Utility Model Laid-Open No. 49764/1973. In this prior art, a trolley adapted to run on the girder is connected through a rope to a rope support which is also adapted to run on the girder. In operation, the trolley runs towing the rope support, while paying off or taking up the rope from and into the trolley so as to suitably adjust the distance between the trolley and the rope support. In this prior art, it is necessary to extend the rope connecting the trolley and the rope support along the girder. Therefore, this arrangement cannot be adopted in the crane of the type in which the structure is flexed at its intermediate portion. In addition, the smooth running of the trolley is impaired due to the necessity for towing the rope support.